1. Field of the Invention
The embodiments of the invention relate to a display, and more particularly, to a liquid crystal display and method of driving the same. Although embodiments of the invention are suitable for a wide scope of applications, it is particularly suitable for preventing a flicker phenomenon of a liquid crystal display driven while driving with a black data insertion method.
2. Discussion of the Related Art
Active matrix type liquid crystal displays display a moving picture using a thin film transistor (TFT) as a switching element. The active matrix type liquid crystal displays have been implemented televisions as well as display devices in portable devices, such as office equipment and computers, because of the thin profile of an active matrix type liquid crystal displays. Accordingly, cathode ray tubes (CRT) are being replaced by active matrix type liquid crystal displays.
A blur phenomenon occurs in which a moving picture displayed on the screen of a liquid crystal display is not clear and blurry because of hold characteristics of the liquid crystal material. As shown in FIG. 1, the CRT provides data to cells by causing a phosphor to emit light for a very short period of time so as to display an image in an impulse drive manners. On the other hand, the liquid crystal display, as shown in FIG. 2, displays an image in a hold drive manner by supplying data to liquid crystal cells during a scan period and by holding data charged to the liquid crystal cells during the remaining field period (or a frame period).
Because the CRT displays the moving picture in the impulse drive manner, as shown in FIG. 3, a perceived image which a viewer perceives as clearer. On the other hand, as shown in FIG. 4, in the liquid crystal display, light and darkness of a perceived image which a viewer feels are not clear and blurry because of the hold characteristics of liquid crystals. A difference between the perceived images of the CRT and the liquid crystal display is caused by an integral effect of an image temporarily held in eyes following a movement. Accordingly, even if the liquid crystal display has a fast response time, the viewer watches a blurry image because there is a difference between the movement of the eyes and a static image of each frame. A black data insertion (BDI) method has been proposed so as to improve the motion blur phenomenon. In the black data insertion method, after video data is written on the screen, the liquid crystal display is driven in an impulse drive manner by supplying black data to the screen.
As an example of the black data insertion method, a screen is division-driven by dividing the screen into a plurality of blocks, and each block is driven by going through a data voltage write operation, a data hold operation, and a black data insertion operation in the order named. In the related art black data insertion method, a black data insertion percentage is fixed irrespective of a frame rate. The black data insertion percentage, as shown in FIG. 5, is defined by a rate of 1-frame period occupied by a black data insertion period in terms of percentage.
Since the related art black data insertion method fixes the black data insertion percentage irrespective of the frame rate, a flicker phenomenon in which a display screen appears to flicker occurs when the frame rate changes. For example, it is assumed that there is a liquid crystal display in which three frame frequencies of 50 Hz, 60 Hz, and 75 Hz are supported and a black data insertion percentage is fixed at 30%. As shown in FIG. 6, because a black data insertion period is about 3.99 ms at the frame frequency of 75 Hz (13.33 ms), a flicker level is low to the extent that a viewer does not recognize the flicker phenomenon. However, because black data insertion percentage is fixed at 30%, a black data insertion period increases to 6.0 ms when the frame frequency falls to 50 Hz. Accordingly, the related art black data insertion method generates the flicker phenomenon when the frame frequency is decreased.